Coil testing apparatus



Sept. 3, 1940. -c. PAUL$ON 2,213,848

COIL TESTING" APPARATUS I Filed Dec. 9, 1959 wvmron 6'. PAUASON A TTORA/f) Patented Sept. 3, 1940 213343 UNITED STATES PATENT OFFICE COIL TESTING APPARATUS Christian Paulson, Elmhurst, 111., assignor to Western Electric Company, Incorporated, New York, N. Y., a corporation of New York Application December 9, 1939, Serial No. 308,401

Claims. (01. 175-183) This invention relates to coil testing apparawinding P and secondary winding S is utilized tus and more particularly to an apparatus for by connecting two opposed windings; for examdetermining the ratio of the number of turns in ple, the secondary and tertiary windings S and the primary as compared with the secondary T in one arm of a bridge circuit and comparing '5 and tertiary windings of induction coils. them with the other winding, in this case the prio It is an object of the present invention to promary winding P. vide a simple apparatus for determining the ratio An induction coil widely used in telephone subof the number of turns in the windings of elecscribers sets has approximately five hundred trical apparatus having a plurality of related turns in its secondary winding, approximately '0 windings. three hundred turns in its tertiary winding and 10 In accordance with one embodiment of the inapproximately six hundred turns in its primary Vention as applied to induction coils used in telewinding. Since the secondary winding S and phone circuits, two of the windings of a coil untertiary winding T are wound oppositely, these der test are connected into one arm of a bridge two windings, connected in series, will, in effect,

5 circuit and the third winding thereof is conhave approximately two hundred turns of effec- 16 nected to the mutual arm of the bridge circuit, tive winding, which should compare with the apwhereupon a motor driven variable resistance proximate six hundred turns of the primary automatically and cyclically varies the resistance winding P as one to three. Accordingly, the opof the mutual arm of the bridge circuit through posite arms of the bridge circuit used in testing 20 a predetermined range and lumped resistance is these coils must also have the ratio of one to 20 added step by step to the ratio arm of the bridge three and the standard arm 9, therefore, has a circuit each time the motor driven variable reresistance of approximately 1,000 ohms and the. sistance moves through its range and fails to ratio arm has a resistance ID of approximately balance the bridge. Control circuits are pro- 3,000 ohms.

vided whereby the failure of the bridge to bal- It has been found to be desirable to utilize a 900 25 ancevafter all of the resistance has been added cycle, 65 volt alternating current for supplying into the ratio arm will cause a signal to be actupotential to the bridge circuit and, accordingly a ated and whereby, if the bridge balances at any 0 cycle Source H provided d is 6011- point during the cycle of the apparatus, further nected to the bridge circuit at the points It! and testing will be discontinued and a signal will be I3. Connected across the bridge circuit is a 30 given that the windings of the coil under test suitable amplifier and rectifier unit [4 having have the proper ratio with respect one to another. its output connected to a galvanometer type re- A better understanding of the invention may be lay [5, which, upon the bridge passing through had by reference to the following detailed dea condition of balance, will cause its needle [6 scription of a circuit for checking the ratio of the to complete a circuit from ground at ll, 35

number of turns in the windings of an induction through the winding of a relay l8, to grounded coil when considered in conjunction with the battery at H], indicating that the bridge accompanying drawing, wherein the single figure has passed through a condition of balance. One represents, diagrammatically, a testing circuit of the input leads of the amplifier and rectifier 40 made in accordance with the present invention. M is connected to the point 20 of the bridge and 40.

Referring to the drawing, wherein an inducthe other is connected to a suitable contacting tion coil 1, designed for use in telephone subdevice 2|, which may be connected to a terminal scribers sets, is shown to have three windings, of the induction coil 1 in any suitable manner, the primary Winding, secondary winding and teras shown diagrammatically. The point l2 of the tiary winding being designated P, S and '1, rebridge circuit may, in a similar manner, be con- 45' spectively. It will be noted that the primary nected to a terminal of the coil 1 under test by winding P and secondary Winding S are wound the contactor indicated at 22 and the primary in the same direction, whereas the tertiary Windwinding of the coil 1 under test may be connected ing T is wound opposite to the primary and secinto the mutual arm of the bridge circuit by a 50, ondary windings P and S. In these coils, the contacting device 23.

ratio of the number of turns in the windings with A motor I is provided for varying the resistance respect one to another is highly critical and in of the mutual arm of the bridge circuit periodithe test set made in accordance with the present cally and is provided with a shaft 24, which drives invention the fact that the tertiary winding T a contact disc 2 and a contactor arm 3 of a varia- 55, is wound in the opposite direction to the primary ble resistance 4. The contact disc 2 has a contact 5 thereon, which, once in each rotation of the shaft 24, will engage a brush 6.

When an induction coil 1 is placed in the testing apparatus forming the subject matter of place ground at 2? on a lead running to a series this invention, it is mounted in a suitable fixture and provision is made whereby the coil being placed in the test set will close a pair of contacts and 2B. The closure of contacts 25 will of relays, to be described more in detail hereinafter, and closure of contacts 26 will connect 3 ground at 28 over the break contact of relay I8,

through the winding of a relay 29, to grounded 1 battery at 38, thereby to energize the relay 29. Relay 28, upon energization, will connect the brush 6 to ground at M and, therefore, when the shaft 24; rotates, it will cause ground to be connected through the brush 6, contact 5, over a lead 32, break contact of a relay 33, the winding of a relay 3 to grounded battery at 35, thereby energizing the relay 34, which will close all of its 1 associated contacts and will remain locked to ground am through its left-hand niakecontacts and the winding of relay 33. Relay 33 will not be energized over the circuit through the contact of relay 3G until contact between contact 5 and 1 brush 6 breaks due to the fact that the winding 1 of relay 33 will have ground connected to both with relay 3 and transfer lead 32 from assoof its ends. As soon as contact 5 and brush 6 are disengaged, relay 33 will pull up in series ciation with relay 34 into association with a relay 38, whereby, upon the next engagement of the contact 5 with brush 6, relay 36 will be energized unless relay 29 falls back to disconnect ground at 3! from the brush 6. Relay 29 will fall back 3 when the connection to ground at 28 is broken by the operation of relay l8 due to the bridge 1 circuit having reached a condition of balance.

ratio arm of the bridge. As theshaft 24 rotates,

" of .the apparatus will proceed and the variable When relay 2M pulls up over the circuit from lead 32, .it will connect an adjustable resistance 49 and resistances 4!, d2, 43 and H1 in series in the it will drive the contactor arm 3 through itscycle' to vary the resistance in the mutual arm of the bridge, which includes the primary winding of theinduction coil, variable resistance 4 and a re-. sistance' lfi. As soon as relay 34 operates, it will complete a circuit to a signal lamp 46 to indicate thatthe induction coil 1 is being tested with the resistances ll, d2, 13 and H! in the ratio arm of the bridge.

manner, no further signal lamps will be lighted.

If the bridge fails. to balance with the reand the test will continue.

grounded battery at 35, thereby to energize relay 35 to remove theresistance ll from the. ratio arm of the bridge, whereupon the test cycle resistance t will be varied throughout its range to determine if the bridge will balance with the resistances 42,..43 and it connected in series.

As relay 35 was energized, it closed a circuit to signal lamp 63, thereby to give a visual indication that the test is proceeding with the bridge in the condition just described.

Ifrthe bridge fails to balance under this condition, the brush Band. contact 5 will, the "next.

If the coil is found to be" acceptable With .the bridge connected in this time they engage, complete a circuit over the lead 32 through the make contact of relay 33, make contact of relay ii, break contact of a. relay 5%, Winding of a relay 6! to grounded battery at 35 to energize relay El, which will pull up and look over a circuit similar to that described in connection with relay 3%. The relay Gd will, of

1 course, also be energized over one of the make contacts of relay ill and will be locked operated and its condition will be indicated due to the completion of a circuit through a second of its make contacts completing the circuit to a lamp 52.

If the bridge fails to balance with the resistances 43 and ill in series in the ratio arm of the bridge, the contact 5 and brush 6 will, on the next rotation of the shaft 24, cause the energization of relays M, to thereby light lamp 6G and indicate that the bridge has failed to balance with the relays t3 and lil in the ratio arm of the bridge. The next cycle of theshaft-ZG will, in a manner similar to that described in con nection with the other relays in the chain, cause. relays 5i and 65 to be energized. Relay El, upon energization, will connect a resistance 69 in series with the resistance it in the ratio arm of the bridge and the test will proceed with resist-1 ances 69 and it in the bridge circuit. A lamp it will be lighted to show that the test is now being performed with the resistances 68- and Iii in series and if a condition of balance is reached, the relay it will be energized and will stop. the test, leaving the lights d5, 63, 62, 66 and 10' lighted to indicate that the coil under test is within the prescribed limits and if the bridge fails to balance, the chain of relays will transferv the circuit from lead 32 to relays ii and i2. It should be noted that the relay 5?, upon being. operated, complete a circuit to connect a resistance "E3 in series with the resistance and variable resistance i in the mutual arm of the bridge circuit so that as the test proceeds, the. resistances #15, it and variable resistance 5 will be included in the mutual arm of the bridge circuit, together with the primary winding P of the coil l and that the ratio arm of the bridge will have, as pointed out before, the resistances I0, Hit and a. portion of theadjustable resistance 49 connected in it. If the bridge failsto balance under these conditions, relays TI and 12 will be energized and when relay ii is energized, it will connect a portion of an adjustable resistance 75 in the ratio, arm of the bridge and will close a circuit to light the lamp 16.

If the bridge reaches a condition of balance with resistance 69 and normally shunted portion of theadjustable resistance '15 in the ratio arm of the bridge, the relay l8 will be operated and stop the test.

If the bridge circuit does not balance under any of the hereinbefore described conditions, the-coil under test does not have the proper ratio of turns in its windings and the next revolution of the shaft 24 will cause the lead 32 to be connected through the chain of operated relays 33, 41, 60, 65, 68 and 72 to the winding. of a relay TI. Energization of the relay ll will close its contacts and complete a circuit to signal lamp 18, indicating that the coil under test does not fall within the selected limits and the operator will thus beinformed that the coil is defective and may then. proceed to discard it and place another coil in the test set.

From the foregoing, it will be apparent that the ratio of the number of turns in an induction coil being tested may be determined with a relatively high degree of accuracy, depending upon which of the signal lamps are lighted when the coil is accepted and the bridge circuit balances to stop the test.

It will be noted that the resistances 4|, 42 and 43 are connected in series at the beginning of the test and that, therefore, the ratio arm of the bridge has ohms resistance in addition to the resistance in and that the resistances 4|, 42 and 43 are cut out of the ratio arm of the bridge one at a time so that the resistance of the ratio arm is reduced in increments of 40 ohms from the value of the resistance [0 plus 120 ohms down to the value of the resistance l0 alone and that thereafter the resistance H is connected in the ratio arm and that this resistance is a ohm resistance so that the test proceeds from a mean value, thereby to eliminate as much testing time as possible.

Although a specific embodiment of the invention has been described hereinbefore, it will be understood that modifications may be made thereof without departing from the scope of the invention, which is to be limited only by the appended claims.

What is claimed is:

1. Coil testing apparatus comprising a bridge circuit having a standard arm, a mutual arm, a ratio arm and an unknown arm, means for connecting a winding of a coil under test in the unknown arm, means for connecting a second winding of the coil under test in the mutual arm, means for changing the value of the mutual arm repeatedly through a fixed range, and means for varying the value of the ratio arm in increments every time the mutual arm is varied through its range.

2. Apparatus for determining whether multiwound coils have the proper ratio of turns in their windings comprising an alternating current bridge circuit having a ratio arm and a mutual arm, means for connecting one winding of a coil to be tested in the mutual arm of the bridge circuit, means for connecting another winding of the coil to be tested in the unknown arm of the bridge circuit, a chain of relays operable under control of the bridge circuit for changing the value of the ratio arm of the bridge circuit by increments, and means for varying the mutual arm of the bridge circuit through a fixed range each time the ratio arm is changed.

3. An automatic testing circuit comprising a bridge having a standard arm, an unknown arm, a mutual arm and a ratio .arm, means for connecting windings of a coil to be tested in the unknown arm and mutual arm of the bridge circuit, means for changing the value of the ratio arm of the bridge circuit in increments, said last mentioned means being operable to arrange the ratio arm at its mean value and reduce said value by said increments to the minimum and thereafter arrange the ratio arm at a value one increment above the mean and increase said value by increments, and means for varying the mutual arm through a fixed range each time an increment is added to or taken from the ratio arm.

4. An automatic testing circuit comprising a bridge having a standard arm, an unknown arm, a mutual arm and a ratio arm, means for connecting windings of a coil to be tested in the unknown arm and mutual arm of the bridge circuit, means for changing the value of the ratio arm of the bridge circuit in increments, said last mentioned means being operable to arrange the ratio ments, means for varying the mutual arm through a fixed range each time an increment is added to or taken from the ratio arm, and means associated with the means for changing the ratio arm to indicate the changes effected in the ratio arm.

5. An automatic testing circuit comprising a bridge having a standard arm, an unknown arm, a mutual arm and a ratio arm, means for connecting windings of a coil to be tested in the unknown arm and mutual arm of the bridge circuit, means for changing the value of the ratio arm of the bridge circuit in increments, said last mentioned means being operable to arrange the ratio arm at its mean value and reduce said value by said increments to the minimum and thereafter arrange the ratio arm at a value one increment above the mean and increase said value by increments, means for varying the mutual arm through a fixed range each time an increment is added to or taken from the ratio arm, and means for interrupting the operation of the means for changing the ratio arm whenever the bridge circuit balances.

6. Coil testing apparatus comprising a bridge circuit having a standard arm, a mutual arm, a ratio arm and an unknown arm, means for connecting a winding of a coil under test in the unknown arm, means for connecting a second winding of the coil under test in the mutual arm, means for changing the value of the mutual arm repeatedly through a fixed range, means for varying the value of the ratio arm in increments every time the mutual arm. is varied through its range, and means under control of the bridge circuit for interrupting the operation of the means for varying the value of the ratio arm.

7. Coil testing apparatus comprising a bridge circuit having a standard arm, a mutual arm, a ratio arm and an unknown arm, means for connecting a winding of a coil under test in the unknown arm, means for connecting a second winding of the coil under test in the mutual arm, means for changing the value of the mutual arm repeatedly through a fixed range, means for varying the value of the ratio arm in increments every time the mutual arm is varied through its range, said last mentioned means comprising a chain relay circuit, and means associated with the means for changing the value of the mutual arm to operate said relays seriatim.

8. Apparatus for determining whether induction coils have the proper ratio of turns in their windings comprising a bridge circuit, means for connecting a winding of a coil under test in one arm of said bridge circuit, a variable resistance in another arm of the bridge circuit, means for connecting another winding of said coil in the second mentioned arm of the bridge circuit, means for repeatedly actuating said variable arm of the bridge circuit throughout its range, and means for changing the value of a third arm of the bridge circuit by fixed amounts each time the variable resistance goes through its range.

9. Apparatus for determining whether induction coils have the proper ratio of turns in their windings comprising a bridge circuit, means for connecting two oppositely wound windings of a coil under test in series in one arm of said bridge circuit, a variable resistance in another arm of the bridge circuit, means for connecting another winding of said coil in the second mentioned arm arm, means for connecting one winding of a coil to be tested in the mutual arm of the bridgecirof the bridge circuit, means for repeatedly actuating said variable arm of the bridge circuit throughout its range, and means for changing the value of a third arm of the bridge circuit by fixed amounts each time the variable resistance goes through its range.

10. Apparatus for determining Whether multi- Wound coils have the proper ratio of turns in their windings comprising an alternating current bridge circuit having a ratio arm and a mutual relays in said chain.

CHRISTIAN PAULSON.

tioned means for emitting an impulse to actuate 10 

